Rack-mountable equipment with a high-heat-dissipation module, and transceiver receptacle with increased cooling

ABSTRACT

An electrical connector includes a heat dissipation module with a first end and a second end opposed to the first end and two receptacle connectors located at the second end. The first and second ends define a transceiver-mating direction such that, when a transceiver is inserted into the first end of the heat dissipation module in the transceiver-mating direction, the transceiver mates with one of the two receptacle connectors, and in the heat dissipation module, air flows parallel to the transceiver-mating direction between the first and second ends and flows between the two receptacle connectors.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to rack-mountable equipment with aheat-dissipation module and data interconnects, and also relates to areceptacle that receives an optical transceiver and that has increasedcooling.

2. Description of the Related Art

Electronics racks are standard components for mounting a wide variety ofelectronic components and equipment in data, computing, and/orcommunication systems. Data centers typically have large numbers ofracks, each filled with various pieces of electronic equipment, such asservers. A standard electrical rack has a 19″ width, which can supportassemblies that mount into the rack with a width of 17.25″. Multipleassemblies can be mounted in each rack, one above the other. Theseassemblies typically are supported by a front bezel formed from cut outsin a flat piece of sheet metal that has clearance holes or slots alongits edges to secure the bezel to the rack.

The rack-mountable electronic components often generate heat that needsto be removed from the rack to avoid overheating of the variouselectronic components. Typically cooling is provided by a fan thatforces air across a heat sink that is in thermal contact with thetemperature-sensitive, heat-producing electronic components.

The rapid increase in data storage and high-bandwidth communicationdriven by Internet expansion is increasing the need for denseinterconnection systems in data centers. These data centers aretypically composed of rows of racks of servers. These servers need to bein high-bandwidth communication with other servers in the data centers.The high-bandwidth communication can be supported by either shieldedelectrical cables or increasingly active optical cables. Active opticalcables support longer transmission distances and higher transmissionbandwidths. An active optical cable typically has an optical engineincorporated into a transceiver on at least one end of the cable thattransforms electrical signals into optical signals (transmission (Tx)function) and transforms optical signals into electrical signals(receiver (Rx) function). An electronics rack can have hundreds or eventhousands of interconnections, each of which generates heat that must beremoved from the electronics rack. The inability to remove this heat canresult in accelerated aging and/or premature failure of theinterconnection or other components in the electronics rack. There is aneed to provide a rack mounting system that facilitates high-heatremoval and dense packaging of the interconnections.

FIG. 21 shows a known active optical cable 200 including a cable 201 anda transceiver 203. The transceiver 201 shown in FIG. 21 is compatiblewith SFF-8436 QSFP+ multi-source agreement revision 4.8, Oct. 31, 2013,hereby incorporated by reference in its entirety. Other known types oftransceivers include SFP, QSFP, microQSFP, etc. The transceiver 203 canmate and unmate with receptacles in a rack (the receptacles and the rackare not shown in FIG. 21 ). The receptacles can be mounted to a printedcircuit board (PCB). Mating the transceiver 203 to the receptaclecreates mechanical and electrical connections. Electrical signals can betransported between the receptacle and the PCB. The transceiver 203includes a pull tab 202 and an edge card 204. The pull tab 202 isoptional and can be used to unmate the transceiver 203. The edge card204 can mate with a connector within the receptacle. The edge card 204can transport electrical signals to/from the transceiver 203.

The transceiver 203 can be optical, electrical, or hybrid of optical andelectrical. If the transceiver 203 is optical, then the cable 201includes optical fibers that transport, in which transport means receiveand/or transmit, optical signals. The optical fibers can be single-modeor multimode fibers. The transceiver 201 can include an optical enginefor transforming optical signals to electrical signals and/or electricalsignals into optical signals.

If the transceiver 203 is electrical, then the cable 201 includeselectrically conductive wires that transport electrical signals. Thecable 201 can be, for example, coaxial cable, which is sometimesreferred to as coax and which includes a single conductor surrounded bya dielectric and a shield layer, and twinaxial cable, which is sometimesreferred to as twinax and which includes two conductors surrounded by adielectric and shield layer. The cable 201 can also include othersuitable transmission lines. The transceiver 201 can include containelectronic circuitry that transport electrical signals, including, forexample, high-bandwidth electrical signals.

If the transceiver is a hybrid, then the cable 201 includes both opticaland electrical cables. The transceiver 203 includes both an opticalengine that transforms optical signals into electrical signals and/orelectrical signals into optical signals and electronic circuitry thatare appropriate for transmitting and/or receiving electrical signalsfrom the electrical cable.

There is an increasing need for smaller transceivers that can be moretightly packed together and higher bandwidth transceivers. However, aschannel density and bandwidth increased, the heat generated by thetransceiver increases, which can cause excessive temperatures in thetransceiver. Excessive temperatures can lead to premature failure andpoor performance. Thus, there is a need for a transceiver receptaclethat provides improved cooling for densely packaged, high-bandwidthtransceivers.

FIGS. 22-24 show a known receptacle 205 that can be used with anelectronics rack. The receptacle 205 can be mounted to a rack mount,which can then be mounted to an electronics rack. The receptacle 205includes a cage 216 with mounting pins 217 and receptacle connectors 220within the cage connected to wafers 222. Each wafer 222 is a module thatincludes a molded insert and a lead frame. The lead frame includeselectrical contacts that each provide an electrical path fortransmitting electrical signals. The molded insert is molded around thelead frame so that the electrical contacts are fixed with respect toeach other within the wafer 222. The wafers 222 can be inserted into thereceptacle connector 220 such that the wafers 222 are arrangedside-by-side to each other so that the electrical contacts of adjacentwafers 222 are fixed with respect to each other in the receptacleconnector 220. The cage 216 includes electromagnetic shields 218,faceplate 219, and slots 211. Transceivers can be inserted into theslots 211 to engage with the receptacle connectors 220. The receptacleconnectors 220 are connected to wafers 222 that block or impede airflow.

During operation, the electronic components of the transceivers generateheat, which is mostly dissipated through the upper and lower walls, witha small amount being dissipated through the side walls. The heatdissipated into the passage 207 cannot be adequately removed because thewafers 222 block the flow of air in a direction from faceplate 219 toreceptacle connector 220. As shown in FIG. 23 , it is known to use holesin the sides of the cage 216. The location and size of the holesrestrict the amount of air that is available to move through the cage216 for cooling, particularly when a transceiver is inserted into thecage 216. But these side holes do not effectively remove the heat withinthe passage 207 (FIG. 22 ) and thus do not effectively remove heat fromthe transceivers. For interior transceivers in arrays 3×2 and bigger,the holes in the sides are not effective or adequate because the heathas to flow from an interior passage to an exterior passage with thesides holes. If the heat in the passage 207 cannot be adequatelyremoved, the transceivers can undergo accelerated aging and/orprematurely fail. Thus, there is need for a receptacle with improvedheat management.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of thepresent invention provide an air-cooled heat sink that is located in thefront bezel of a rack. Robust physical contact is provided between theheat sink and the heat generating components of the interconnectionsystem, including, for example, the transceiver of an active opticalcable. The robust physical contact and large heat dissipating surface ofthe heat sink provide a low impedance thermal path between thetransceiver and the ambient environment. In addition to providing heatdissipation, the heat sink can also serve as an electromagneticradiation shield, reducing radiated stray electromagnetic radiationoutside of the rack enclosure.

To overcome the problems described above, preferred embodiments of thepresent invention provide a receptacle with a cage that can be mountedto a PCB and with a receptacle connector in the cage. Electricalconnections between the PCB and the receptacle are made by flyovercables. A transceiver can be mated and unmated to the receptacle.

An electrical connector according to a preferred embodiment of thepresent invention includes a heat dissipation module with a first endand a second end opposed to the first end and two receptacle connectorslocated at the second end. The first and second ends define atransceiver-mating direction such that, when a transceiver is insertedinto the first end of the heat dissipation module in thetransceiver-mating direction, the transceiver mates with one of the tworeceptacle connectors, and in the heat dissipation module, air flowsparallel to the transceiver-mating direction between the first andsecond ends and flows between the two receptacle connectors.

The two receptacle connectors are preferably vertically stacked inrelation to a base substrate. The two receptacle connectors preferablyeach receive a card-edge of a mating transceiver. Preferably, the heatdissipation module includes a cage, and the cage further defines twoslots that extend between the first and second ends, and the air flowsbetween the slots. The two receptacle connectors are preferablyelectrically isolated from one another.

Preferably, the two receptacle connectors each include a housing,high-speed and low-speed electrical contacts in the housing, high-speedcables electrically connected to the high-speed electrical contacts, andlow-speed cables and a power filter electrically attached to thelow-speed electrical contacts.

The electrical connector further preferably includes a heat sink locatedbetween the two receptacle connectors. The heat sink preferably is anextrusion or bent sheet metal. The heat sink preferably defines air flowpaths. The heat sink is preferably mounted to the heat dissipationmodule such that a position of the heat sink is fixed when thetransceiver is mated with the one of the receptacle connectors. Channelsin the heatsink are preferably no larger than one quarter of awavelength of a dominant emitted electromagnetic interference generated,when the transceiver is mated with the transceiver, by electricalsignals transmitted and/or received by the transceiver.

A blower is preferably mounted adjacent to the heat sink such that theblower directs forced air over the heat sink. Air preferably flows inone or more air-flow paths between the two receptacle connectors.

Only the cage is preferably configured to be press-fit or surfacemounted to a substrate.

An electrical connector according to a preferred embodiment of thepresent invention includes a housing, high-speed and low-speedelectrical contacts in the housing, high-speed cables electricallyconnected to the high-speed electrical contacts, and low-speed cablesand a power filter electrically attached to the low-speed electricalcontacts.

Preferably, high-speed is at least 25 Gbits/sec data transmission speed,and low-speed is less than 25 Gbits/sec data transmission speed.

An electrical connector system according to a preferred embodiment ofthe present invention includes a cage with a first end and a second endopposed to the first end, and two electrical connectors located at thesecond end. The first and second ends define a transceiver-matingdirection such that when a transceiver is inserted into the first end ofthe cage in the transceiver-mating direction the transceiver mates withone of the two electrical connectors, and in the cage, air flowsparallel to the transceiver-mating direction between the first andsecond ends and flows between the two electrical connectors.

Preferably, the cage includes press-fit tails, and the two electricalconnectors do not include press-fit tails, through-hole tails, orsurface-mount tails. Preferably, the two electrical connectors arereceptacle connectors each including a signal conditioner electricallyconnected to cables. Preferably, only the cage is configured to bepress-fit or surface mounted to a substrate.

An electrical connector system according to a preferred embodiment ofthe present invention includes a cage with a first end and a second endopposed to the first end, and two electrical connectors located at thesecond end. The first and second ends define a transceiver-matingdirection such that, when a transceiver is inserted into the first endof the cage in the transceiver-mating direction, the transceiver mateswith one of the two electrical connectors, and the two electricalconnectors are spaced apart from each other such that, in the cage, airflows parallel to the transceiver-mating direction between the first andsecond ends and flows between the two electrical connectors.

The electrical connector system further preferably includes a heat sinklocated between the two electrical connectors. Preferably, air flows inone or more air-flow paths between the two electrical connectors.

A rack mount according to a preferred embodiment of the presentinvention includes an electrical connector or an electrical connectorsystem according to the various preferred embodiments of the presentinvention. An electronics enclosure according to a preferred embodimentof the present invention includes one or more rack mounts of accordingto various preferred embodiments of the present invention.

A preferred embodiment of the present invention includes a QSFPelectrical connector and cage according to SFF-8438, in which the QSFPelectrical connector is an edge-card connector that is devoid ofpress-fit or mounting tails. A preferred embodiment of the presentinvention includes a stacked QSFP electrical connector and a cage, inwhich the stacked QSFP type of electrical connector includes anedge-card connector that is devoid of press-fit or mounting tails.

An electrical connector system according to a preferred embodiment ofthe present invention includes a substrate, a first cage with a firstend and a second end opposed to the first end and mounted to a firstside of the substrate, a first electrical connector located at thesecond end of the first cage, a second cage with a first end and asecond end opposed to the first end and mounted to a second side of thesubstrate opposite the first side, and a second electrical connectorlocated at the second end of the second cage. The first and second endsof the first and second cages define a transceiver-mating direction suchthat, when a transceiver is inserted into the first end of the first orsecond cage in the transceiver-mating direction, the transceiver mateswith the first or second electrical connectors, and air flows parallelto the transceiver-mating direction between the first and second ends ofboth the first and second cages.

An electrical connector system according to a preferred embodiment ofthe present invention includes a cage with a first end and a second endopposed to the first end and with a slot extending between the first andsecond ends, an electrical connector located at the second end, and aheat sink or a heat spreader rigidly attached to the cage. The first andsecond ends define a transceiver-mating direction such that, when atransceiver is inserted into the slot at the first end of the cage inthe transceiver-mating direction, the transceiver mates with theelectrical connector, and when a transceiver is inserted into the slot,the transceiver is pushed against a side of the slot in the cageadjacent the heat sink or the heat spreader.

Preferably, a spring pushes the transceiver against the side of theslot.

An electrical connector system according to a preferred embodiment ofthe present invention includes a cage with a first end and a second endopposed to the first end and with a slot that extends between the firstand second ends, and an electrical connector located at the second end.The first and second ends define a transceiver-mating direction suchthat, when a transceiver is inserted into the slot at the first end ofthe cage in the transceiver-mating direction, the transceiver mates withthe electrical connector, and the electrical connector mechanicallyfloats in a direction orthogonal or substantially orthogonal to thetransceiver-mating direction and does not mechanically float in adirection parallel or substantially parallel to the transceiver-matingdirection.

The electrical connector is preferably removed using a tool insertedinto the first end of the slot.

An electrical connector system according to a preferred embodiment ofthe present invention includes a substrate, a cage connected to thesubstrate, including a first end and a second end opposed to the firstend, and including a slot that extends between the first and secondends, and an electrical connector located at the second end. The firstand second ends define a transceiver-mating direction such that, when atransceiver is inserted into the slot at the first end of the cage inthe transceiver-mating direction, the transceiver mates with theelectrical connector, and the distance between the electrical connectorand substrate is allowed to float and a flexible electrical connectionconnects the electrical connector and the substrate.

An electrical connector according to a preferred embodiment of thepresent invention includes a heat dissipation module with a first endand a second end opposed to the first end, two receptacle connectorslocated at the second end, and a passageway that extends from the firstend to the second end and that is positioned adjacent to one of the tworeceptacle connectors. The first and second ends define atransceiver-mating direction such that, when a transceiver is insertedinto the first end of the heat dissipation module in thetransceiver-mating direction, the transceiver mates with one of the tworeceptacle connectors, and in the heat dissipation module, heat in thepassageway travels through the passageway parallel to thetransceiver-mating direction and escapes through the first and secondends.

The above and other features, elements, characteristics, steps, andadvantages of the present invention will become more apparent from thefollowing detailed description of preferred embodiments of the presentinvention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a portion of rack mount according to apreferred embodiment of the present invention.

FIG. 2A is a front view of the rack mount shown in FIG. 1 .

FIG. 2B is a perspective view of the rack mount shown in FIG. 1 .

FIG. 3 is a perspective view of a portion of a heat-dissipation moduleshown in FIG. 1 .

FIG. 4 is a schematic cross-section of a portion of a rack mount in abelly-to-belly configuration according to a preferred embodiment of thepresent invention.

FIGS. 5A, 5B, and 5C are schematic cross-sections of a portion of a rackmount in a stacked configuration according to a preferred embodiment ofthe present invention.

FIG. 6 shows a schematic cross-section of a portion of a rack mount in abelly-to-belly configuration with electrical connectors according to apreferred embodiment of the present invention.

FIG. 7 is a perspective view of heat-dissipation module made of sheetmetal according to a preferred embodiment of the present invention.

FIG. 8 is a perspective view of a receptacle according to a preferredembodiment of the present invention.

FIG. 9 is a perspective view of a transceiver and a receptacle connectoraccording to a preferred embodiment of the present invention.

FIG. 10 is a rear perspective view of a receptacle connector beingplugged into the cage.

FIG. 11 is a front perspective view of the receptacle connector.

FIG. 12 is a top exploded view of a receptacle connector.

FIG. 13 is a rear perspective view of the receptacle connector.

FIG. 14 is a rear perspective view of an alternative receptacleconnector.

FIG. 15 is a front perspective view of a cage according to a preferredembodiment of the present invention.

FIG. 16 is a perspective view of a tool according to a preferredembodiment of the present invention.

FIG. 17 is a perspective view of a receptacle with a blower according toa preferred embodiment of the present invention.

FIG. 18 is a perspective view of the blower shown in FIG. 17 .

FIG. 19 is perspective sectional view of the receptacle.

FIG. 20 is a side sectional view of the receptacle shown in FIG. 19 .

FIG. 21 shows a prior art active cable.

FIG. 22 is perspective sectional view of a known receptacle.

FIG. 23 is rear perspective view of the known receptacle shown in FIG.22 .

FIG. 24 is a side sectional view of the known receptacle shown in FIG.22 .

FIG. 25 is a perspective sectional view of a receptacle with a heatsink.

FIG. 26 is a perspective sectional view of a receptacle withheat-transferring fins.

FIGS. 27-29 are perspective views of a receptacle with a double-walledcage.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A preferred embodiment of the present invention provides a low-impedancethermal path between a transceiver and the ambient environment. Heattransfer to the ambient environment is provided by forced convective airflow across a heat sink. The heat sink is incorporated into the frontbezel of a heat-dissipation module that can be mounted to an electronicsrack. The heat sink can provide cooling for a plurality of transceivers.This contrasts with many prior art transceivers in which the heat sinkis incorporated directly into the transceiver. The preferred embodimentsof the present invention advantageously provide superior cooling for alarge number of transceivers that are densely connected in anelectronics rack.

FIG. 1 shows a portion of rack mount 60. The rack mount 60 includes aheat-dissipation module 10, a printed circuit board (PCB) 50, a heatsink 12, a transceiver 30, and a cable 31. The transceiver 30 ispreferably an optical transceiver, and the cable 31 is preferably anoptical cable. The transceiver 30 can use one of many industry standardtransceiver formats such as QSFP+, PCIe, CXP, CFP, SFP, etc. Inparticular, the transceiver 30 can meet the requirement of SFF-8438(INF-8438i, Rev. 1.0, hereby incorporated by reference in its entirety).The preferred embodiments of the present invention are not limited tothese standard transceiver formats, and any transceiver can be usedincluding proprietary transceivers or developing transceiver formats,such as OSFP and mini-OSFP. The OSFP format, Octal Small Form-FactorPackage, supports 8 fully duplexed communication channels. That is, theformat has 8 independent transmission channels and 8 independentreceiver channels. Incorporated into any of these transceiver formatscan be a silicon photonic element that provides modulation and/orreceive functions; however, this is not a requirement. In FIG. 1 , thetransceivers 30 are shown adjacent to their respective mating slot 11 inthe heat-dissipation module 10. In operation, the transceivers 30 can beplugged into their respective slots 11. The rack mount 60 does not needto include spring-biased heat sinks. The heat sinks 12 can be formeddirectly by the heat-dissipation module 10 and not separate finnedstructures positioned behind a front bezel or a panel of a system or arack.

For clarity, the PCB 50 shown in FIG. 1 is not populated with anyelectronic components; however, in practice the PCB 50 can have variouselectronic components that support high-speed computing andcommunication. The PCB 50 can be connected to a plurality ofheat-dissipation modules 10. Each module 10 includes a heat sink 12, acage 16, and a slot 11 for a transceiver 30. The heat-dissipation module10 is described in more detail below. Connected in the slots 11 of theheat-dissipation module 10 can be one or more transceivers 30. In FIG. 1, four transceivers 30 are connected to each module; however, the modulecan be configured to accept more or less than four transceivers 30. Eachtransceiver 30 is connected to a cable 31 that provides communicationbetween the PCB 50 and some other element in a data network. Aspreviously mentioned, the transceiver 30 is preferably an opticaltransceiver, and the cable 31 is preferably an optical cable thatcontains one or more optical fibers. In FIG. 1 , four heat-dissipationmodules 10 are connected to the top the PCB 50, and fourheat-dissipation modules 10 are connected to the bottom of the PCB 50.Each heat-dissipation module 10 is capable of accepting fourtransceivers 30 so a total of 32 transceivers can be connected to thePCB 50 as shown in FIG. 1 . The transceivers 30 mounted above the PCB 50can make electrical connections to the top of the PCB 50, and thetransceivers 30 mounted below the PCB 50 can make electrical connectionsto the bottom of the PCB 50. This transceiver configuration is referredto as “belly-to-belly” and allows for short electrical paths between thetransceiver 30 and the PCB 50 facilitating transmission ofhigh-bandwidth signals, such as, 10 Gbps, 28 Gbps, 56 Gbps, or evenhigher bandwidths.

FIG. 2A shows an end view of a portion of a rack mount 60. In FIG. 2A,the transceivers 30 have been removed for clarity. FIG. 2A shows eightheat-dissipation modules 10. Each heat-dissipation module 10 has slots11 for four transceivers 30. Each slot 11 is surrounded by an electricalconductor, such as a metal, forming a cage 16 that provideselectromagnetic shielding between transceivers 30 situated in adjacentslots 11. The PCB 50 is not clearly visible in FIG. 2A, but would besituated between the upper and lower rows of heat-dissipation modules 10as shown in FIG. 1 . Connectors, which would be mounted to the PCB 50 toaccept each transceiver 30, are also not shown in FIG. 2A. Eachheat-dissipation module 10 has a heat sink 12 including a web ofmaterial with air passages running completely through the heat sink 12along a front to back transceiver insertion direction. In FIG. 2A, thetransceiver insertion direction extends into the drawing page. The heatsink 12 associated with each heat-dissipation module 10 provides coolingfor all four transceivers 30 that can be mounted in the slots 11. Thetransceivers 30 themselves do not need any type of finned structure todissipate heat into the surrounding atmosphere because they are cooledby conduction to the heat sink 12 of the heat-dissipation module 10 andperhaps forced air blowing through the heat sinks 12 along thetransceiver insertion direction. Electromagnetic shielding (not visiblein FIG. 2A) can be provided between the heat-dissipation modules 10 toreduce stray electromagnetic radiation.

FIG. 2B shows a perspective view of a rack mount 60 with aheat-dissipation module 10. Four heat-dissipation modules 10 aresituated above an edge of PCB 50 and four heat-dissipation modules 10are situated below an edge of the PCB 50. The heat-dissipation modules10 are fully populated with transceivers 30. A cable 31 is connected toeach transceiver 30, and each transceiver 30 can have a pull ring 32 foreasy removal from the heat-dissipation module 10. Flanges 15 can belocated on the sides of the heat-dissipation module 10 to secure therack mount 60 to the sides of an electronics rack. Representativedimensions for a rack mount 60 are shown in FIG. 2B. Rack mount 60 canbe compatible with mounting in a 19-inch rack. The height rack mount 60can be approximately 1.375 inches, and the opposing sides of the mountedtransceivers 30 can be separated by approximately 0.582 inches. Thesedimensions are compatible with the heat-dissipation module 10 occupying1 U of rack height (1 U=1 rack unit=1.75″ high). These values areexemplary only, and the dimensions can be adjusted as required to bestsuit the intended application. In practice, many of these rack mounts 60can be stacked one above the other in an electronics rack.

FIG. 3 shows a single heat-dissipation module 10. The heat-dissipationmodule 10 includes slots 11 for four transceivers 30 and a heat sink 12.The slots 11 can include latching features, not shown in FIG. 3 , thathelp to secure a plugged transceiver 30 in position. The slots 11 canalso include flexible members, not shown in FIG. 3 , that lightly slideagainst the sides of the transceiver 30 to provide electromagneticshielding. The heat sink 12 includes a web of material providing a largesurface area for convective heat transfer of air flowing through theheat sink 12. In FIG. 3 , the air is depicted as flowing out the heatsink 12 in direction A; however, the air direction can be reversed, i.e.the front-to-back transceiver insertion direction instead ofback-to-front as shown. A fan (not shown in FIG. 3 ) can be mounted onthe front, back, or sides of the heat-dissipation module 10, althoughthis is not a requirement. A fan can be mounted somewhere else in theelectronics rack (not shown in FIG. 3 ) that supports theheat-dissipation module 10. Instead of a fan, a duct can bring forcedair to the electronics rack. The fan or duct can then draw or force airthrough the heat sink 12 along direction A or along the transceiverinsertion direction (180 degrees opposite of direction A). The heat sink12 webbing can be designed so that it is thicker in the region of theheat sink 12 adjacent to the slot 11 to provide enhanced thermalconductance to regions of the heat sink 12 farther away from the slot11. A hexagonal web pattern is shown in FIG. 3 ; however, the webpattern can take many forms such as squares, rectangles, diamonds,triangles, serpentine, etc. The web pattern also need not be a regularpattern, but could have a random structure. The heat sink 12 provides alarge surface area for convective heat transfer and a low-impedanceconductive path between the transceiver 30 and the convective surfacearea.

The heat-dissipation module 10 can be fabricated from a metal extrusionor from sheet metal. The heat-dissipation module 10 can be made ofaluminum, copper, steel, or some composite of these materials; however,any material that has high electrical and thermal conductivity can beused. A coating or surface treatment can be applied to the materialforming the heat-dissipation module 10. Electrical conductivity isimportant because the heat sink 12 can help provide electromagneticshielding to reduce electromagnetic interference (EMI) between the manytransceivers 30 that can populate an electrical rack and to reduce strayEMI outside of the rack to acceptable levels. To provide adequate EMIshielding, gaps between the webbing of the heat sink 12 should be lessthan a quarter of the shortest wavelength of interest in the radiatedelectromagnetic energy spectrum. For a system operating at 28 Gbps theEMI is predominately emitted up to a frequency of 14 GHz, so that a gapbetween the web elements can be approximately 5 mm or less. For unitswith higher frequencies of interest, the gaps can be proportionallysmaller to achieve a similar level of shielding. The depth d of the heatsink 12 should be adequate to completely cover the electrical connectioninto the PCB 50 to provide effective EMI shielding and provide foradequate heat transfer. Thermal modeling indicates that the depth d ispreferably between 20 mm and 60 mm, although shorter and longer depthscan be used. The height h of the heat sink 12 can also be chosen toprovide adequate heat transfer as well as a compact design so that thebelly-to-belly transceiver configuration shown in FIG. 2A can be mountedin a 1 U (1 U=1 rack unit=1.75″ high) rack opening. Thermal modelingindicates that a height h of approximately 18 mm should provide adequatethermal dissipation and fit within a 1 U rack opening. Smaller or largerheights h can be used, for example, if the system is designed to fitinto a 2 U rack opening or to accommodate different connector ortransceiver sizes in different configurations.

FIG. 4 shows a rack mount 60 with a belly-to-belly configuration. Upperand lower connectors 20 a, 20 b are mounted to the top and bottom of PCB50, respectively. The upper connector 20 a provides electrical pathsbetween the upper transceiver 30 a and PCB 50. Similarly, the lowerconnector 20 b provides electrical paths between the lower transceiver30 b and the PCB 50. These electrical paths can use one or more centralconductors surrounded as much as possible by an electrically groundedshield to maximize transmission and minimize distortion of highbandwidth signals transmitted along the electrical connectors. Both theupper and lower transceivers 30 a, 30 b are pluggable and can mate andunmate with their respective electrical connector 20 a, 20 b. Upper andlower cables 31 a, 31 b are attached to the upper and lower transceivers30 a, 30 b, respectively. These cables 31 a, 31 b transmit and/orreceive data.

Also shown in FIG. 4 are two springs 14 a, 14 b. The springs 14 a, 14 bensure robust physical contact between the heat sink 12 a, 12 b and thetransceivers 30 a, 30 b, which are the major heat generating components.The springs 14 a, 14 b force the upper and lower transceivers 30 a, 30 bagainst their respective heat sinks 12 a, 12 b. This ensures alow-impedance thermal path between the transceivers 30 a, 30 b and theheat sinks 12 a, 12 b, minimizing the operational temperature of thetransceivers 30 a, 30 b. It is generally desirable to operate thetransceivers 30 a, 30 b at temperatures as close to room temperature aspossible. Operating temperatures equal or less than 30° C. above anambient data center environment are generally acceptable. Thermalmodeling has indicated that the design shown in FIG. 4 provides heatdissipation well in excess of this requirement. The modeling indicatesthat the transceiver operating temperature can be approximately 6° C.above ambient for a 5 watt heat load from each transceiver 30 a, 30 b.Providing better cooling and a lower transceiver operating temperatureadvantageously increases the operating lifetime of any laser diodes inthe upper and lower transceivers 30 a, 30 b. While the springs 14 a, 14b are shown as leaf springs in FIG. 4 , the springs 14 a, 14 b can takemany forms, or the force between the transceivers 30 a, 30 b and heatsinks 12 a, 12 b can be provided by some other mechanism that ensuresrobust physical contact between the transceivers 30 a, 30 b and the heatsink 12 a, 12 b.

An advantage of the belly-to-belly configuration shown in FIG. 4 is thatboth the upper and lower transceiver 30 a, 30 b are located adjacent tothe PCB 50 such that the electrical paths between the transceivers 30 a,30 b and PCB 50 is short. This allows transmission of high-bandwidthsignals with minimal loss and interference. However, other suitableconfigurations can be used. Although upper and lower connectors 20 a, 20b are shown as PCB mounted board connectors, connectors 20, 20 b canalso be cable connectors that include cable connectors as shown in FIG.8 .

FIGS. 5A-5C show alternative stacked configurations. In these stackedconfigurations, the lower transceiver 30 b is adjacent to the PCB 50,and the upper transceiver 30 a is positioned above the lower transceiver30 b farther from the PCB 50. The upper and lower transceivers 30 a, 30b are connected to upper and lower cables 31 a, 31 b, respectively.

As shown in FIGS. 5A and 5B, the lower connector 20 b can be identicalor similar to the lower connector 20 b in FIG. 4 in which the lowerconnector 20 b is directly connected to the PCB 50. In FIG. 5A, abovethe lower transceiver 30 b is a lower heat sink 12 b, which serves todissipate heat generated in the lower transceiver 30 b. A lower spring14 b forces the lower transceiver 30 b against the lower heat sink 12 b,ensuring a low impedance thermal path between them. An upper spring 14a, which can be identical or different than the lower spring 14 b, ispositioned between the lower heat sink 12 b and the upper transceiver 30a. The upper spring 14 a can also be positioned so it is fully containedinto the heat-dissipation module 10. The upper spring 14 a forces theupper transceiver 30 a against the upper heat sink 12 a, ensuring a lowimpedance thermal path between them. The upper heat sink 12 a serves todissipate heat generated in the upper transceiver 30 a. An upperconnector 20 a mates with the upper transceiver 30 a. Flyover cables 22provide an electrical path between the upper connector 20 a and the PCB50. The cables 22 can be any suitable shielded electrical connections,including one or more coaxial, or twin axial cables. The cables 22 canbe rigid, semi-ridge, or flexible. Flexible twin axial, i.e. twinax,cable is preferably used because it readily allows propagation ofdifferential high-speed electrical signals and can be easily routed toany location on the PCB 50 with minimal loss and distortion. The cables22 can fly over the PCB 50 as described in commonly assigned U.S.provisional patent application 62/131,989, which is hereby incorporatedby reference in its entirety. An advantage of the stacked configurationis that all the high-speed electrical connections can be made on asingle side of the PCB 50. Also, the component height on the PCB 50 canbe approximately twice as high compared to that available in thebelly-to-belly configuration. Another advantage of this preferredembodiment is that both the upper and lower heat sinks 12 b can beformed monolithically in a single extrusion step.

In FIGS. 5B and 5C, the heat-dissipation module 10 includes a singleheat sink 12. A lower spring 14 b forces the lower transceiver 30 bagainst the heat sink 12, ensuring a low impedance thermal path betweenthem, and an upper spring 14 a, which can be identical or different thanthe lower spring 14 b, forces the upper transceiver 30 a against theheat sink 12, ensuring a low impedance thermal path between them. InFIG. 5B, the lower connector 20 b is connected directly to the PCB 50,and the upper connector 20 a is connected to the PCB 50 by cables 22. InFIG. 5C, the lower connector 20 b is connected to the PCB 50 by cables22 b, and the upper connector 20 a is connected to the PCB 50 by cables22 a. It is also possible that the lower connector 20 b includes someelectrical paths that are directly connected to the PCB 50 as shown inFIG. 5B and some electrical paths that are connected to the PCB 50 bycables 22 b as shown in FIG. 5C.

FIG. 6 shows a portion of a rack mount 60 with a belly-to-bellyconfiguration with connectors 20 a, 20 b attached to heat sinks 12 a, 12b. This preferred embodiment is similar to that shown FIG. 4 , and so,only the differences between the figures will be described. A differencebetween the preferred embodiment shown in FIG. 4 and the preferredembodiment shown in FIG. 6 is the mounting of the connectors 20 a, 20 b.In FIG. 4 , the connectors 20 a, 20 b are connected directly to the PCB50. As mentioned above, this has the advantage of providing a short,rigid electrical path between the connectors 20 a, 20 b and the PCB 50.However, this fixed, rigid mounting can result in an unfavorabletolerance stack up. In some cases it can be difficult to force thetransceivers 30 a, 30 b to be flush with the heat sinks 12 a, 12 b whilethey are simultaneously mating with the connectors 20 a, 20 b. Thepreferred embodiment shown in FIG. 6 solves this problem. In FIG. 6 ,the upper and lower connectors 20 a, 20 b are mounted on the upper andlower heat sinks 12 a, 12 b, respectively. The upper and lowerconnectors 20 a, 20 b can be mounted to surfaces 19 a, 19 b of heatsinks 12 a, 12 b so that the upper and lower connectors 20 a, 20 b canmove in directions parallel to surfaces 19 a, 19 b of the heat sinks 12a, 12 b. Similarly the connectors 20 a, 20 b can be mounted within thelength of the heat dissipation module 10 in such a way, with guides orgrooves for examples but not so limited, that the connectors 20 a, 20 bare free to move in a direction parallel or substantially parallel tosurface 19 a, 19 b of the heat sinks 12 a, 12 b. The connectors 20 a, 20b in FIG. 6 are, however, constrained in a direction parallel orsubstantially parallel to the insertion direction of the transceivers 30a, 30 b, which is perpendicular or substantially perpendicular tosurfaces 19 a, 19 b. This mounting configuration allows the connectors20 a, 20 b to float in directions perpendicular or substantiallyperpendicular to the transceiver mating direction, but be rigidlyconstrained in the mating direction. Because the connectors 20 a, 20 bcan float in a vertical direction, the springs 14 a, 14 b can force thetransceivers 30 a, 30 b against their respective heat sinks 12 a, 12 bwith little concern for possible lack of contact between thetransceivers 30 a, 30 b and heat sinks 12 a, 12 b because of tolerancestack up. Because the upper and lower connector positions relative tothe PCB 50 in this preferred embodiment are no longer fixed, cables 22a, 22 b similar to those described in relation to FIG. 5C can be used toprovide the electrical paths between the connectors 20 a, 20 b and PCB50. It is also possible that the connectors 20 a, 20 b can include someelectrical paths that are directly connected to the PCB 50 as shown inFIG. 4 and some electrical paths that are connected to the PCB 50 bycables 22 a, 22 b as shown in FIG. 6 .

Further configurations are possible. Both the belly-to-bellyconfiguration shown in FIGS. 1, 2, 4, and 6 and the stackedconfiguration shown in FIGS. 5A-5C have the major surfaces, i.e.,surfaces with the largest surface areas, of the transceivers 30, 30 a,30 b parallel or substantially parallel to the plane of the PCB 50. Thisis not a requirement. The major surfaces of the transceivers 30, 30 a,30 b can be oriented perpendicular or substantially perpendicular withinmanufacturing tolerances to the PCB plane. In this case, a flyover styleelectrical connection can be made to the PCB 50 as described in commonlyassigned U.S. patent application Nos. 62/136,059, 62/107,671, and Ser.No. 14/845,990, which are each hereby incorporated by reference in theirentirety. In these perpendicular configurations, heat sinks can beprovided adjacent at least one of the major surfaces of thetransceivers. In the stacked configuration, the position of the uppertransceiver 30 a and the upper heat sink 12 a can be reversed, so thatthe lower and upper heat sinks 12 b, 12 a are adjacent to each other.Depending on the PCB component layout, these various configurations canbe mixed and matched in any system to achieve an optimal layout tomaximize signal integrity, thermal performance, density or othermetrics, or any combinations thereof, for all channels in thecommunication network.

As previously mentioned, a heat-dissipation module 10 can be formed fromsheet metal. FIG. 7 shows a sheet-metal heat-dissipation module 10. Theoverall layout is similar to that shown for an extruded heat-dissipationmodule 10 shown in FIG. 3 . The heat-dissipation module 10 has a numberof slots 11 to accept transceivers 30. Surrounding each slot 11 is acage 16 to minimize EMI between the transceivers 30 and any circuitry. Aheat spreader 13 is adjacent the top of the cage 16. The heat spreader13 can be formed from a solid piece of metal and serves to distributeheat generated by transceivers 30 (not shown in FIG. 7 ) to the heatsink 12. The heat sink 12 can be formed from a web of bent-and-cut sheetmetal. In FIG. 7 , the web is shown as having square openings to allowair passage through the heat sink 12. As previously described, airpassages of other shapes can be used. The heat-dissipation module 10 hasa plurality of mounting pins 17 which connect to a PCB (not shown inFIG. 7 ). The sheet-metal heat-dissipation module 10 can be arranged inany of the above-described preferred embodiments. An advantage of thesheet metal formed heat-dissipation module 10 is that it can be cheaperand easier to manufacture than an extruded heat-dissipation module 10.

Instead of optical transceivers, electrical transceivers can be used.Also independent transmitters and/or receivers can be used instead of atransceiver. The placement of various components in the system can alsobe varied. For example, FIG. 4 shows the non-mating ends of the upperand lower transceivers 30 a, 30 b substantially flush with the end ofthe PCB 50. This is not a requirement. The transceivers can extend pastthe end of the PCB 50 or be recessed such that the end of the PCB 50extends past the transceiver ends. The component placement has oftenbeen described in terms of an upper and lower component. It should beappreciated that these terms are relative to the PCB mountingorientation and can be exchanged or substituted by left/right dependingon the orientation.

Preferred embodiments of the present invention also include a receptaclethat can receive one or more transceivers and that includes a cage andelectrical connectors in the cage. The electrical connectors can includeboth high- and low-speed cables that flyover a PCB to differentlocations on the PCB. Using low-speed cables provides additional spacebetween the slots in a multi-slot cage, which allows increased airflowbetween the transceivers, improving cooling and heat management of thetransceivers. The electrical connectors can be plugged into the rear ofthe cage. The electrical connectors can include latches that engage withlatch slots in the cage. A blower can be used to improve cooling. Heatsinks (with or without forced air) can be provided in the extra space toimprove cooling. A fluid-cooled heat sink, such as a heat pipe, can beprovided in the extra space to further improve cooling.

An electrical-connector removal tool can be inserted into the front ofthe cage assembly to remove an electrical connector from the cage.

FIG. 8 shows a receptacle 100 according to a preferred embodiment to thepresent invention. The receptacle 100 includes a cage 116 with fourslots 111 arranged in two rows. Each slot 111 can accept one transceiver130. FIG. 8 shows three slots 111 mated with three transceivers 130 andone slot 111 that is empty. The bottom of the cage 116 includes mountingpins 116 that allow the receptacle 100 to be mounted to a PCB (not shownin FIG. 8 ). The receptacle 100 can include an optional a faceplate 119between the upper and lower slots 111. The faceplate 119 can include aplurality of openings or louvers that allow air flow through thefaceplate 119, through passageway 107 (FIG. 19 ), between receptacleconnectors 120 (FIG. 19 ), and over cables 122. Stated another way, theopenings or louvers are fluidly connected to an opening defined by thepassageway 107 between receptacle connectors 120. The passageway 107 canextend from the first end to the second end and can be positionedadjacent to one of the two receptacle connectors. Air can also flow overthe cables 122, between the receptacle connectors 120, through thepassageway 107, and through the faceplate 119. In non-forced airsystems, heat can escape from the passageway 107 through the first andsecond ends or through the faceplate 119 openings and a second-endopening positioned between the receptacle connectors 120. Stated anotherway, heat in the passageway can travel through the passageway 107parallel to the transceiver-mating direction and escape through thefirst and second ends. The passageway 107 can be positioned adjacent andparallel to one of the slots 111, positioned between and parallel to twoadjacent slots 111, or be positioned adjacent and parallel to at leastone receptacle connector 120. The cage 116 can include a plurality ofelectromagnetic interference (EMI) shields 118 around its perimeter tolimit radiated EM fields. The height of the cage 116 assembly can becompatible with mounting cage 116 and attached PCB within a 1 U rackopening. The receptacle 100 can be mounted in an electronics rack. Thereceptacle 100 includes cables 122 that extend from the rear of the cage116. The cables 122 can transmit both high and low speed signals betweenthe receptacle 100 and a PCB.

The transceiver 130 includes a cable 131 that transmit signals to andfrom the transceiver 130. The transceiver 130 can include a pull tab 132that can be used to remove the transceiver 130 from the receptacle 130.The cables 131 flyover the PCB. The benefits of using of flyover cablesfor high-speed signals is described in commonly assigned U.S. patentapplication Nos. 62/136,059, 62/107,671, and Ser. No. 14/845,990.

FIG. 9 shows a transceiver 130 and receptacle connector 120. Thereceptacle connector 120 is located within the cage 116 shown in FIG. 8. The transceiver 130 is mated to the receptacle 100 by inserting thetransceiver 130 into the receptacle 100 such that the edge card 134 isinserted into the receptacle connector 120. The cables 122 extend fromthe rear of the receptacle connector 120. The cables 122 can beterminated to contacts in the receptacle connector 120 and to the PCB,creating an electrical path between the receptacle connector 120 and thePCB. The transceiver 130 can use one of many industry standardtransceiver formats such as QSFP+, PCIe, CXP, CFP, SFP, etc. Inparticular, the transceiver 30 can meet the requirements of SFF-8438(INF-8438i, Rev. 1.0).

FIG. 10 shows a receptacle connector 120 being plugged into the rear ofthe cage 116. FIGS. 11-13 show the receptacle connector 120. Thereceptacle includes a clip 128, a lead frame 124, and a housing 125. Thehousing 120 can be made of any suitable electrically insulatingmaterial, such as molded plastic. The lead frame 124 is inserted intothe housing 120 and is kept in place with the clip 128. The lead frame124 includes an overmold over the cables 122 and the contacts 123 a, 123b. The upper contacts 123 a mate with electrical lands on the top of theedge card 134 of the transceiver 130, and the lower contacts 123 b matewith electrical lands on the bottom of the edge card 134 of thetransceiver 130. Any number of contacts 123 a, 123 b can be used. It isalso possible to only use the upper contacts 123 a or the lower contacts123 b.

The clip 128 includes latches 121. When the receptacle connector 120 isinserted into the cage 116, the latches 121 engage with latch slots 103in the cage 116. Although FIG. 11 shows two latches 121 on top and twolatches 121 on bottom, any number and any location of latches 121 can beused. The clip 128 can also include openings 129 that engage with bosses126 on the housing 125 when the clip 128 is connected to the housing125. The clip 128 can be made of stamped and formed sheet metal. Theclip 121 can include one or more openings for the cables 122.

As shown in FIG. 13 , the cables 122 can include high-speed cables 122 aand low-speed cables 122 b. Any number of high-speed 122 a and low-speedcables 122 b can be used. The high speed cables 122 a can transmit, forexample, high-bandwidth signals in excess of 10 Gbps and can include,for example, twinax, coax, triax, or some other suitable electricaltransmission line. In some applications, high speed is at least 25Gbits/sec data transmission speed, and low speed is less than 25Gbits/sec data transmission speed. Low-speed cables 122 b can transmit,for example, control signals and power and can include, for example, aninsulated wire without a ground shield. One end of the cables 122 a, 122b can be terminated to a corresponding contact 123 a, 123 b, the otherend of the cables can be terminated to the PCB. If the cables 122 a aretwinax, then the two center conductors of the twinax can be terminatedto adjacent signal contacts and the shield can be connected to a groundcontact(s).

FIG. 14 shows an alternative receptacle connector 120 that includes aPCB assembly (PCBA) 127. PCBA 127 can include electrical components thatprovide signal and/or power conditioning and/or filtering. PCBA 127 canimprove the performance and simplify the design of the transceiver 130because the power and control signals will have less electrical noise.

FIGS. 15, 19, and 20 show the cage 116. The cage 116 can includemounting pins 117 that can be used to mount the cage 116 to a PCB (a PCBis not shown in FIG. 15 ). The mounting pins 117 can be“eye-of-the-needle” type suitable for press-fit mounting. The receptacleconnectors 120 do not need to have any mounting pins, including, forexample, press-fit pins, through-hole pins, surface-mount pins, etc., tomount the receptacle connector 120 to the PCB. The cage 116 includeswalls 106 that define slots 111. Although four slots 111 in a 2×2 arrayare shown in FIG. 15 , the cage 116 can include any number of slots 111in any arrangement. For example, the cage 116 can have two slotsarranged in 1×2 array (horizontally spaced along a substrate) or in a2×1 array (vertically stacked with respect to a substrate). The walls106 can include latches 104 that engage the transceiver 130 when thetransceiver 130 is mated with the receptacle 100. Similar to springs 14a, 14 b in FIGS. 4-6 , each slot 111 could include one or more springsto press the transceiver 130 toward the passage 107 to ensure robustphysical contact between the transceiver 130 and the passage 107. Thecage 116 can be made in any suitable manner, including being made ofstamped and formed metal.

As shown in FIG. 19 , the cage 116 also includes a passage 107 thatprovides an air-flow path. The passage 107 allows air to flow betweenthe front of the receptacle 100 (where the transceivers 130 can beplugged in) and the rear of the receptacle 100 (where the receptacleconnectors 120 are plugged in). When transceivers 130 are plugged intothe top and bottom slots 111 in the receptacle, air can flow between thetop and bottom transceivers 130 and from front to back (or back tofront) of the receptacle, cooling the heat-producing transceivers 130.The front of the passage 107 can include a faceplate 119 (faceplate 119is not shown in FIG. 15 but is shown in FIGS. 19 and 20 ), and the rearof the passage 107 can be uncovered. By not using wafers, the receptacleconnectors 120 can be arranged to not block or to minimize impeding theair flow completely through both opposed ends of the passage 107 suchthat air passes fluidly through the faceplate 119, through the passage107, and between the receptacle connectors 120. The cables 122 can bearranged to not block or impede air flow. In addition to not blockingair flow, the cables 122 provide better signal integrity than that thewafers 222 used in the known receptacle 205. Thus, an air-flow path fromthe front to the back (or from the back to the front as described above)of the receptacle 100 can be provided.

Instead of having an open passage 107 as shown in FIGS. 15, 19, and 20 ,the passage 107 could include heat-transferring fins similar to the fins171 shown in FIG. 26 that extend from the wall adjacent to thetransceiver 130 into the interior of the passage 107 or could include aheat sink such as heat sink 162 shown in FIG. 25 . The hexagonal patternof such can provide multiple air paths from the front to the back of thereceptacle 100. The webbing could have a constant thickness or couldhave a variable thickness. For example, the webbing could be thicker atthe top and bottom and thinner near the middle.

The cage 116 can include a light pipe 105 in the passage 107. As shownin FIG. 15 , each passage 107 can include two light pipes 105. The lightpipes 105 can transmit light from an LED on a PCB to the front of thereceptacle 100. The cross-sectional area of the light pipes 105 ispreferably less than 15% of the total cross-sectional area of thepassage 107. For example, a passage 107 can have a cross-sectional areaof 450 mm², and the light pipes 105 can have a cross-sectional area of25 mm². If there are two light pipes 105 per passage 107, then the totalcross-section of the two light pipes is 50 mm², which is about 11% ofthe total cross-sectional area of the passage 107.

The cage 116 of FIG. 15 can be used with the stacked configurationsshown in FIGS. 5B and 5C. If the receptacle connectors 120 includecables 122, then the cage 116 can be used in the stacked configurationshown in FIG. 5C. If the bottom receptacle connector 120 provides directelectrical paths to the PCB, then the cage 116 can be used in thestacked configuration shown in FIG. 5B. Other configurations are alsopossible. For example, if the bottom receptacle connectors 120 includescables 122 and direct electrical paths to the PCB, then the cage 116 canused in a stacked configuration that is a combination of FIGS. 5B and5C.

FIG. 25 shows receptacle 100 with a cage 166. Cage 166 is similar tocage 116 but includes a heat sink 162 in the passage 107 and is doublewalled. The heat sink 162 extends along the passage 107. The frontopening of the passage 107 can be covered by faceplate 119, and the rearopening of the passage can be covered by faceplate 169. It is notnecessary to use faceplates 119, 169 separate from the heat sink 162. Itpossible that the faceplates 119, 169 are part of the heat sink 162. Theheat sink 162 can be similar to the heat sink 12 shown in FIG. 3 with,for example, hexagonal webbing. Other webbing patterns are alsopossible. The heat sink 162 defines air flow paths between the front andrear of the passage 107.

The cage 166 includes four slots 111 arranged in a 2×2 array. Othernumbers and arrangements of slots 111 can also be used. The two columnsof slots 111 are separated by an interior double wall defining a passagebetween the columns of slots 111. The opening of the passage between theinterior double walls is covered by faceplate 168 with holes. Thefaceplate plate 168 can be separate from faceplate 119 or can beconnected to faceplate 119 as a single unitary body. The size and shapeof the holes in faceplate 168 can be the same or can be different fromthe holes in faceplate 119. Holes 167 are arranged in the top of thecage 166 along the passage between the interior double walls. The sizeand shape of holes 167 can be the same as or can be different from thesize and shape of the holes in the faceplate 168.

As shown in FIG. 25 , the exterior walls of the cage 166 can be a doublewall. Only one exterior double wall is shown in FIG. 25 because FIG. 25is a sectional view. As with the interior double wall, the exteriordouble walls can be covered by a faceplate 168 with holes and caninclude holes 167 along the top of the cage 166. Holes in faceplate 168can be fluidly connected to a cavity between adjacent slots 111. Thecavity can extend from the faceplate 168, through the cage 166, and tothe optional rear faceplate 169. Alternatively, or in addition, holes infaceplate 168 can be fluidly connected to holes 167. The exterior doublewalls can include holes 167 (not shown in FIG. 35 but shown in FIG. 27 )adjacent to passages 107 to provide air flow through the exterior doublewalls and at the bottom of the exterior double wall to provide air flowat the bottom of the of exterior double wall. The interior double wallscan include similarly arranged holes. Although not shown in FIG. 25 , itis possible to add top and bottom exterior double walls to cage 166 sothat each slot 111 has passages on four sides.

FIG. 26 shows receptacle 100 with cage 116. Cage 116 in FIG. 26 includesfins 171 extending into the passage 107. Fins 171 can help intransferring heat from transceivers in the slots 111 to the passage 107.Any number, size, and shape of fins 171 can be used. The faceplate 119in FIG. 26 includes a hole through which the light pipe 105 extends. Theend of the light pipe 105 can be flush or substantially flush with thefront of the receptacle 100.

FIGS. 27-29 show receptacle 100 with cage 166. Cage 166 in FIGS. 27-29is similar to cage 166 shown in FIG. 25 but without the heat sink 162.In FIG. 27 , the cage 166 includes faceplates 119, 168, and in FIG. 28 ,the cage 166 is without faceplates 119, 168. FIG. 28 shows light pipes105 in the interior and exterior double walls. Although FIG. 28 showsfour light pipes 105 (two in one exterior double wall and two in theinterior double wall), any number and any arrangement of light pipes 105can be used. The cage 166 includes two exterior double walls and oneinterior double wall. Cage 166 can include double walls that extendacross the top and bottom of the cage 166. A different arrangement ofdouble walls could be used with a different array of slots 111. Forexample, a 2×3 array of slots 112 could include two interior doublewalls and two exterior double walls. As shown in FIG. 28 , the doublewalls, both interior and exterior, can include holes 167 adjacent topassage 107. The double walls can also include holes 167 near the bottomof the double walls. The top of the cage 166 can also include holes 167over the passages defined by the double walls. Although not shown inFIG. 28 , the passage 107 could also include fins similar to fins 171 inFIG. 26 .

FIG. 29 shows two rear faceplates 169. Any number and any arrangement offaceplates 169 can be used depending on the arrangement of the slots111. The size and shape of the holes can be the same as or can bedifferent from the size and shape of the holes in the faceplates 119,168.

Air can be forced through passage 107 to increase the cooling of thetransceivers 130. If the receptacle 100 is included on a rack mount inan electronics rack, then a fan mounted on the rack mount or in theelectronics rack can force air through the passage 107. It is alsopossible, that as shown in FIG. 17 , the receptacle 100 includes ablower 140 attached to the cage 116. FIG. 18 shows the blower 140. Theblower 140 includes a guide 141 to direct the blown air. As shown inFIG. 18 , the blower 140 can receive air in direction C and blow the airout in direction D through guide 141 into holes in the outer wall of thecage 116. Each of the three fingers of the guide 141 can direct air intoone of the passages 107 connected to the top, middle, and bottomfaceplates 119 a, 119 b, 119 c. In this manner, blower 140 can blowambient air through the passages 107 and over the transceivers 130. Theblower 140 can also blow air in the opposite direction, from within thereceptacle 100 to the outside ambient air. The blower 140 can also beused, possibly with ducting, if there is a heat sink in the passage 107.Any suitable blower can be used. The blower 140 could be a 30-mmdiameter fan with rotating blades, a piezoelectric actuated fan, acorona (ion) fan, etc. Instead of being mounted to the exterior of thecage 116, the blower 140 could be mounted within one or more of thepassages 107.

In addition to blower 140, FIG. 17 also shows other possiblearrangements of the receptacle 100. For example, the slots 111 can bearranged in a 2×4 array so that the receptacle can receive eight totaltransceivers 130. Instead of a single faceplate 119, the receptacle 100can include a top faceplate 119 a, a middle faceplate 119 b, and abottom faceplate 119 c. Each faceplate 119 a, 119 b, and 119 c covers aseparate passage that allows air to flow from front to back (or back tofront) of the receptacle 100. This arrangement is similar to the stackedarrangement shown in FIG. 5A but with an additional heat sink locatedbetween the PCB 50 and the lower transceiver 30 b and lower connector 20b. In such an arrangement, the lower connector 20 b would include cables22 b to provide electrical paths from the lower connector 20 b and thePCB 50.

If the cages 116 shown in FIGS. 8 and 17 are the same height, then theslots 111 in FIG. 17 are closer together than the slots 111 in FIG. 8 .

The cage can include a liquid-filled heat pipe that facilitates heattransfer away from transceiver mated with the cage. The heat pipe can beused to spread the heat from localized heat sources, such as the opticalengine of the transceiver 130. For example, the heat spreader 13 shownin FIG. 7 can include a heat pipe to facilitate heat transfer between atransceiver in the slot 11 and the heat sink 12. The heat pipe allowsthe thickness of the heat spreader to be reduced, reducing weight andincreasing the available area for the heat sink.

FIG. 16 shows a receptacle-connector removal tool 190. To remove areceptacle connector 120, the receptacle-connector removal tool 190 isinserted into a slot 111 from the front side of the cage 116 as shown,for example, in FIG. 26 . Upper beveled surface 191 a and lower beveledsurface 191 b elastically deform the clip 128 so that latches 121disengage from the latch slots 103. Continuing to pushreceptacle-connector removal tool 190 into slot 111 will push thereceptacle connector 120 out of the back the cage 116. The ability torework or replace a receptacle connector 120 with a simple tool providesflexibility and ease in system maintenance and debugging. No desolderingof any connection is required to remove receptacle connector 120, andthus there is little chance of inadvertent damage during the removaloperation.

It should be understood that the foregoing description is onlyillustrative of the present invention. Various alternatives andmodifications can be devised by those skilled in the art withoutdeparting from the present invention. Accordingly, the present inventionis intended to embrace all such alternatives, modifications, andvariances that fall within the scope of the appended claims.

What is claimed is:
 1. An electrical connector system comprising: a cageincluding: a first slot that includes a first end and a second endopposed to the first end of the first slot; a first electrical connectorlocated at the second end of the first slot; a second slot that includesa first end and a second end opposed to the first end of the secondslot; a second electrical connector located at the second end of thesecond slot; a single heat sink located between the first and the secondslots; and a low impedance thermal path between the single heat sink andeach of the first and the second slots.
 2. The electrical connectorsystem of claim 1, wherein the first and the second ends of the firstand the second slots define a transceiver-mating direction; and both ofthe first and the second electrical connectors mechanically float in adirection orthogonal or substantially orthogonal to thetransceiver-mating direction and do not mechanically float in adirection parallel or substantially parallel to the transceiver-matingdirection.
 3. The electrical connector system of claim 1, furthercomprising a first cable including a first end connected to the firstelectrical connector.
 4. The electrical connector system of claim 1,further comprising a second cable including a first end connected to thesecond electrical connector.
 5. The electrical connector system of claim1, wherein both of the first and the second electrical connectors aredevoid of press-fit or mounting tails.
 6. The electrical connectorsystem of claim 1, wherein, when the electrical connector system isconnected to a substrate: a first flexible electrical connectionconnects the first electrical connector and the substrate; and a secondflexible electrical connection connects the second electrical connectorand the substrate.
 7. The electrical connector system of claim 1,wherein the first slot is configured to receive a first transceiver, andthe second slot is configured to receive a second transceiver.
 8. Theelectrical connector system of claim 7, wherein, when the firsttransceiver is inserted into the first slot and the second transceiveris inserted into the second slot, each of the first and the secondtransceivers physically contacts the single heat sink.
 9. The electricalconnector system of claim 7, wherein when the first transceiver isinserted into the first slot, the first transceiver pushes against aside of the first slot adjacent to the single heat sink; and when thesecond transceiver is inserted into the second slot, the secondtransceiver pushes against a side of the second slot adjacent to thesingle heat sink.
 10. The electrical connector system of claim 7,wherein the first slot includes a first spring that pushes the firsttransceiver against the single heat sink, and the second slot includes asecond spring that pushes the second transceiver against the single heatsink.
 11. The electrical connector system of claim 7, wherein the singleheat sink is fixed with respect to the cage.
 12. The electricalconnector system of claim 1, wherein the single heat sink includes airpassages running completely through the single heat sink.
 13. Theelectrical connector system of claim 1, wherein the single heat sinkprovides convective heat transfer to air flowing through the single heatsink.
 14. The electrical connector system of claim 1, wherein the singleheat sink is fluid-cooled.
 15. An electronics rack comprising: aheat-dissipation module including a front bezel; and the electricalconnector system of claim 1, wherein the single heat sink is included inthe front bezel.
 16. A heat dissipation module comprising: an upper slotconfigured to receive an upper transceiver; a lower slot configured toreceive a lower transceiver; and a single heat sink located between theupper and the lower slots; wherein when the upper transceiver isinserted into the upper slot, the upper transceiver is forced againstthe single heat sink; when the lower transceiver is inserted into thelower slot, the lower transceiver is forced against the single heatsink.
 17. The heat dissipation module of claim 16, further comprising:an upper electrical connector located at a first end of the upper slot;and a lower electrical connector located at a first end of the lowerslot.
 18. The heat dissipation module of claim 17, wherein each of theupper and lower electrical connectors mechanically floats in onedirection and does not mechanically float in a direction orthogonal tothe one direction.
 19. The heat dissipation module of claim 16, whereinthe heat sink is fluid-cooled.
 20. A heat dissipation module comprising:a cage that includes upper and lower slots; a single heat sink locatedbetween the upper and the lower slots; an upper spring located on a sideof the upper slot opposed to the single heat sink; and a lower springlocated on a side of the lower slot opposed to the single heat sink. 21.The heat dissipation module of claim 20, further comprising: an upperelectrical connector located at a first end of the upper slot; and alower electrical connector located at a first end of the lower slot. 22.The heat dissipation module of claim 21, wherein each of the upper andthe lower electrical connectors mechanically floats in one direction anddoes not mechanically float in a direction orthogonal to the onedirection.
 23. The heat dissipation module of claim 20, wherein the heatsink is fluid-cooled.